Process of whitening acrylic fibers



FIPSSD? XR 3&4621258 3,462,238 PROCESS OF WHITENING ACRYLIC FIBERS Julian J. Hirshfeld and Bertie Joseph Reuben, Decatur, Ala., assignors to Monsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Apr. 7, 1966, Ser. No. 540,842 Int. Cl. D011 3/10 U.S. Cl. 8-140 5 Claims ABSTRACT OF THE DISCLOSURE Acrylic fibers are made to appear whiter and brighter by contacting them with an aqueous solution containing a nitrogen-containing compound selected from the group consisting of sulfamic acid, and alkali metal and alkaline earth salts of sulfamic acid.

This invention concerns a process of treating acrylic fibers to make the fibers appear whiter. More particularly, the invention relates to a process of treating acrylic fibers with sulfamic acid or a salt of sulfamic acid to make them appear whiter and brighter.

Fibers, filaments and other shaped articles produced from acrylonitrile polymers have a tendency to develop an undesirable color change, i.e. the articles tend to yellow when exposed to natural sunlight or various types of artificial light. This is especially true during the manufacture of acrylic fibers Where the drying process step appears to yellow or thermally degrade the fiber. Such a color change occurs when the fibers are either in the bleached or the unbleached state and gives an undesirable and unstable background color for the fiber either in dyed or undyed textile end uses. The color change is especially undesirable where the textile articles are to be dyed pastel colors.

During the manufacture of acrylic fibers, the fibers appear to yellow during the drying process step. One theory for this phenomenon is that the drying step tends to thermally degrade the fiber and results in a fiber which appears to have a yellow cast. This yellow cast is an undesirable characteristic in the further processing of the acrylic fiber into textile end uses. The desired acrylic fiber color for processing into textile end uses is a completely white or a blue-white color. To overcome this yellow cast, some textile manufacturers have incorporated optical brightners into the acrylic fibers to give a brighter or whiter cast to the fiber. These optical brightners tend to reflect light off of the textile article and give a bluewhite appearance to the article. However, the use of optical brightners increases the cost of the acrylic fiber.

It is known in the textile art that sulfamic acid and salts of sulfamic acid are useful as fire retardants in textile articles composed of cellulosic fibers. Also, it is known that sulfamic acid is useful as a fixing agent for textile dyes. The use of sulfamic acid and salts of sulfamic acid as whitening agents for textile articles comprised of acrylic fibers is however unexpected.

It is therefore an object of this invention to provide a process of brightening or whitening textile articles comprised of acrylic fibers.

It is another object of this invention to provide textile articles comprised of acrylic fibers having a brighter or whiter color.

Another object of this invention is to provide a process of minimizing undesirable yellow colors in textile articles comprised of acrylic fibers.

Still another object of this invention is to provide a process of treating acrylic fibers which enhances the use of acrylic fibers for textile end uses.

These and other objects of this invention are accom- 3,462,238 Patented Aug. 19, 1969 plished by providing a process of whitening textile articles comprised of acrylic fibers comprising contacting the article with an aqueous solution containing a nitrogen containing compound selected from the class consisting of sulfamic acid and salts of sulamic acid.

The term textile article is meant to include fiber, yarn, knitted fabrics, woven fabrics, and any article comprised of acrylic fibers. The textile article can also contain minor portions of other fibers, e.g. wool. Acrylic fiber, as used herein is meant to include acrylic fibers and mod acrylic fibers. Preferred acrylic fibers are those obtained from fiber producing polymers containing at least about acrylonitrile units. However, fiber producing polymers containing less than 80% but at least 35% of the acrylonitrile units are also useful with the invention. Preferred fiber producing polymers include polyacrylonitrile, copolymers including binary and ternary polymers containing at least 80% by weight of acrylonitrile units in the polymer molecule and blends comprising polyacrylonitrile or copolymers comprising acrylonitrile with from about 2% to about 50% of another polymeric material, the blend having an overall polymerized acrylonitrile content of at least about 80% by weight.

For example the fiber producing polymer may be a copolymer of from 80 to 98% of acrylonitrile and from 2 to 20% of another copolymerizable mono-olefinic monomer. Suitable copolymerizable mono-olefinic monomers include acrylic, alpha-chloroacrylic and methacrylic acids, the acrylates such as methyl methacrylate, ethyl methacralate, butyl methacrylate, methoxy-methylmethacrylate, beta-chloroethyl methacrylate, and corresponding esters of acrylic and alpha-chloroacrylic acids; vinyl compounds such as vinyl chloride, vinyl fluoride, vinyl bromide, and vinylidene chloride; and l-chloro-l-bromoethylene; methacrylonitrile; acrylamide and methacry1= amide; alpha-chloroacrylamide and monoalkyl substituted products thereof; methyl vinyl ketone; vinyl carboxylates such as vinyl acetate, vin-yl chloroacetate, vinyl propionate, and vinyl stearate; N-vinylimides such as N-vinylphthalimide and N-vinylsuccinimide; methylene malonic esters; itaconic acid and itaconic esters; N-vinylcarbazole; vinyl furan; alkyl vinyl esters; vinyl sulfonic acid; ethylene alpha, beta-dicarboxylic acids and their anhydrides or derivatives such as diethyl citraconate, diethylmesaconate; styrene; vinyl naphthalene; vinyl-sub= stituted tertiary heterocyclic amines such as the vinylpyridines and alkyl-substituted vinylpyridines for example 2-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, etc.; l-vinylimidazole and alkyl-substituted l-vinylimidazoles such as 2, 4-, or S-methyl-l-vinylimidazole, vinyl pyrrolidone, vinylpiperidone, and other mono-olefinic co= polymerizable monomeric materials.

The polymer can be a ternary interpolymer, for example, products obtained by the interpolymerization of acrylonitrile and 2 or more of the above enumerated monomers. More specifically and preferably, the ternary polymers can contain from 80 to 98% of acrylonitrile, from 1 to about 10% of a vinylpyridine or a l-vinylimid azole, and from about 1 to about 16% of another copolymerizable mono-olefinic material such as methacrylo nitrile, vinyl acetate, methyl methacrylate, vinyl chloride. vinyl bromide, vinylidene chloride, and the like.

Also, the polymer can be a blend of polyacrylonitrile or a copolymer of from 30% to 99% acrylonitrile and from about 1% to about 20% of at least one other mono olefinic copolymerizable monomeric material with from 2% to 50% of the weight of the blend of a copolymer of from 30% to of a vinyl substituted tertiary heterocyclic amine and from 10% to about 70% of at least one other mono-olefinic copolymerizable monomer. When the polymeric material comprises a blend, it is preferred that the blend contain from about 80 to 99% of a co polymer of 80% to 98% acrylonitrile and from about 2% to about 20% of another mono-olefinic monomer, such as vinyl acetate, with from about 1% to about 20% of a copolymer of from about 30% to about 90% of a vinyl substituted tertiary heterocyclic amine such as vinyl pyridine, as l-vinylimidazole or vinyl lactam, and from about to about 70% of acrylonitrile to give a dyeable blend having an overall vinyl-substituted tertiary heterocyclic amine content of from about 2% to about 10%, based on the weight of the blend.

The nitrogen containing compound can be sulfamic acid or a salt of the sulfamic acid. Examples of useful nitrogen containing compounds include sulfamic acid, sodium sulfamate, potassium sulfamate, magnesium sulfamate, ammonium sulfamate, calcium sulfamate, calcium methylene sulfamate, calcium benzaldehyde sulfamate, calcium furfural sulfamate. The preferred nitrogen containing compounds are sulfamic acid and ammonium sulfamate.

As stated previously, the textile article comprised of acrylic fibers can be whitened by contacting the article with an aqueous solution containing a nitrogen containing compound selected from the group consisting of sulfamic acid and salts of sulfamic acid. Contacting the article with the solution can be accomplished by padding, exhaust bath, spraying, kiss-roller application, or any other like method. The contacting method should deposit on the fiber from about 0.05% up to about 5% of the nitrogen containing compound. Preferably the fiber should contain from about 0.1% to about 2.4% of the nitrogen containing compound on the fiber. Generally speaking, amounts in excess of about 2.0% produce no additional improvement on the fiber and simply increase the cost of the treatment. After the textile article is contacted with the solution containing the nitrogen containing compound, it is dried, preferably at a temperature above about 212 F.

The treated textile article has a whiter appearance than an untreated similar textile article. The treatment does not adversely affect the handle and feel of the article or cause stiffening of the article. Also, the treatment does not decrease the wearing ability of the textile article and, in general, does not change the original appearance and texture of the textile article. The textile article can be dry cleaned without adversely affecting the treatment given-it by this invention. However, the treated textile article does have limited use in that certain of the above enumerated nitrogen containing compounds are more water soluble than others. Where the treated article is to be subjected to repeated washings in water, it is preferred to use a less water soluble salt of the sulfamic acid in the treatment, e.g., calcium methylene sulfamate.

The following examples are presented to specifically illustrate the invention. To indicate the significance of the invention, i.e., the brighter or whiter color imparted to the samples, photo reflectance measurements are made of the treated samples. The photo reflectance measurements are made by using a Photovolt Reflectance Meter, model No. 610, made by Photovolt Corp., New York City, NY. The reflectance measurements of treated samples are compared to photo reflectance measurements of untreated similar samples. A large photo reflectance measurement indicates a whiter textile article. These examples are not intended to limit in any way the invention. Unless otherwise noted, percents are based on weight.

Example I Samples of uncollapsed acrylic tow composed of 93% acrylonitrile and 7% vinyl acetate are padded at ambient temperature with an aqueous solution containing the following percents of sulfamic acid, percents are based on volume of the solution. The tow is then dried at about 230 F. Thereafter the dried tow is annealed by placing it in a steam chamber, pressuring the chamber with 41 p.s.i.g. steam, and then depressuring the chamberthis is repeated seven times. Photo reflectance measurements TABLE 1 Percent of Photo reflectance Sample sulfamic acid measurements 1 Control 64 2 Test"-.. 0.6 67 3 do.. 1. 8 70 4.-. ...do. 3.0 66 5 ..d0 4. 2 70 Example II A- sample of uncollapsed acrylic tow composed of 76.6% of a copolymer being 93% acrylonitrile and 7% vinyl acetate, 10.4% of acopolymer being 50% acrylonitrile and 50% methylvinylpyridine and 13% polyvinylchloride is padded at ambient temperature with an aqueous solution containing 2% sulfamic acid. The tow i dried at 200240 F. and is annealed as described in Example I except the steam is at 50 p.s.i.g. A photo reflectance measurement of the sample is made and compared to a photo reflectance measurement made of a control sample, i.e., an identical sample treated as described above except it is not padded with the solution containing sulfamic acid. The test sample indicates a measurement 10 points whiter than the control sample.

Example III Samples of acrylic knitted fabric composed of fibers being 93% acrylonitrile and 7% vinyl acetate are padded at ambient temperature with aqueous solutions containing sulfamic acid. The weight percents of sulfamic acid deposited on each sample is indicated in Table 2. The samples are then dried and photo reflectance measurements are made to indicate the whiteness of the samples. Table 2 contains the photo reflectance measurements.

TABLE 2 Percent of sulfamic acid deposited Photo reflectance Sample on sample measurements 1 Control 64 2 est 0.3 67 0.9 70 1. 6 69 2. 1 70 Example IV The whiteness of acrylic fabric samples is improved by padding the samples at ambient temperature with an aqueous solution containing 1% of the following salts of sulfamic acid, the percent based on the weight of the sample. Table 3 indicates the particular salts of the sulfamic acid:

TABLE 3 Sample Sulfamie acid salt 1 Test Ammonium sulfamate.

2 -do. Sodium sulfamate.

. ..do. Potassium sulfamate.

do Magnesium sulfamate.

Example V Thereafter, the fiber is dried, crimped, and processed into stable fibers. Photo reflectance measurements are made on twelve samples of this fiber and the average photo reflectance measurement is indicated below in Tabl 4 as Sample No. 1.

(2) Samples of staple acrylic fiber are obtained by the above process except the finish bath contains in addition thereto 0.1% of sulfamic acid, based on the weight of the fiber. Photo reflectance measurements are made on 8 samples of this fiber and the average measurement is indicated in Table 4 as Sample No. 2.

(3) Samples of staple acrylic fiber are obtained by the above process except the finish bath composition contains 1.6% of the above standard textile finish composition and 0.1% ammonium sulfamate, the percents based on the weight of the fiber. Photo reflectance measurements are made on 8 of the samples and the average measurement is indicated in Table 4 as Sample No. 3. Table 4 contains the sample number, the finish bath composition and the average photo reflectance measurements:

position. 0.1% ammonium sulfam ate.

While the invention has been described with particular reference to specific embodiments, it is to be understood that it is not limited thereto, but is to be construed broad ly' and resricted solely by the scope of the appended claims i What is claimed is:

1. A process of whitening textile articles comprised of acrylic fibers comprising contacting the article with an aqueous solution of a nitrogen-containing compound selected from the group consisting of sulfamic acid, alkali metal salts of sulfamic acid, and alkaline earth salts of sulfamic acid, so as to deposit on said article from about 0.5% to about 5.0 based on the weight of the article of said nitrogen-containing compound; and drying the article.

2. The process of claim 1 wherein the nitrogen-containing compound is sulfamic acid.

3. The process of claim 1 wherein the nitrogen-con taining compound is selected from the group consisting of sodium sulfamate, potassium sulfamate, magnesium sulfamate, ammonium sulfamate, calicum sulfamate, calcium methylene sulfamate, calcium benzaldehyde sulfamate, and calcium furfural sulfamate.

4. The process of claim 1 wherein the nitrogen-containing compound is ammonium sulfamate.

5. The process of claim 1 wherein from about 0.1% to about 2.0% of the nitrogen-containing compound is deposited on the textile article, the percents being based on the weight of the article References Cited UNITED STATES PATENTS 2,751,277 6/1956 Coover 8-107 3,083,070 3/1963 Schoateden 8115.5 3,089,748 5/1963 Mogensen 8-1155 MAYER WEINBLATT, Primary Examiner US. Cl. X.R. 8-89, 102, 107,109

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Julian J Hirshfeld et a1 ied that error appears in the abqve identified It is certif ters Patent are hereby; corrected as patent and that said Let shown below:

Column 3 line 30 "2 .4%" should read 2. 0%

Signed and sealed this 17th day of November 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer WILLIAM E. SCHUYLER, JR. 

